A Manhattan financial trader says sexism — not her relationship to an accused Ponzi scheme mastermind — spurred her firing from a top Street firm, according to her gender-discrimination suit.

Lindy Boville — once a rising hot shot at Royal Bank of Canada Capital Markets — says her boss used her affair with disgraced hedge fund manager James Nicholson as a pretext to boot her and reassign her lucrative accounts to male colleagues.

She owned up to a steamy relationship with Nicholson, who allegedly operated Westgate Capital Management as a classic Ponzi scheme, but said business and pleasure never mixed.

“RBC does not terminate men who display bad judgment in their personal lives, even in extreme circumstances,” according to her lawsuit filed in Manhattan federal court. The suit seeks unspecified damages.

Nicholson was arrested in February for losing $150 million of investors’ money in his alleged fraud.

She said she was derided with outbursts like, “Do the curtains match the carpet?” and “Did that dress shrink at the dry cleaners?” Male colleagues, the suit said, constantly referred to her “guns” for breasts and “wheels” for legs while propositioning her non-stop.

Boville earned between $7 million and $8 million a year in commissions and was never reprimanded for her performances, according to the suit.

RBC said Boville was working behind the scenes to help Nicholson’s business.

“Ms. Boville showed poor judgment in helping Jim Nicholson raise money for his hedge fund and failing to disclose her activities to her supervisors,” said Kevin Foster, an RBC spokesman. “It is irrelevant that she had a personal relationship with Nicholson, and she should have told RBC what she was doing.” With Post Wires